Communications systems increasingly use connectionless networks such as internet protocol (IP) networks for example. Connectionless networks comprise a number of network elements such as routers for example, which are connected together according to some topology. Traffic introduced into the network at a network element and destined for another element including an access element at the network periphery for example is directed across the network according to forwarding tables in each of the network elements it passes through. The forwarding tables in each element map the traffics end destination in the network onto a network element directly connected to the current element. In this way traffic across the network makes a series of short hops from network element to network element according to each elements forwarding tables. The forwarding tables are created automatically by distributed software programmes and protocols called routing protocols (eg OSPF or BGP4) as a result of routing guidelines provided by network operators and designers.
Because of the size and complexity of many networks, together with the practical difficulties of predicting traffic flows through the network, congestion points or bottlenecks can result in practical networks. While forwarding tables of network elements can be amended to try to mitigate congestion in other elements, this can have a knock on effect on the rest of the network creating other congestion points for example.